This invention relates to a device used on needling machines for the production of needle-bonded fabric webs or the like, having above the fiber fleece to be needled a holding-down means provided with openings for the needles, said fleece being advanced along a likewise perforated needle plate.
Two parallel perforated plates extending across the entire working width of the machine are located in the needling zone of needling machines. The lower plate is the needle plate into which the needles penetrate in their downward stroke, and the upper plate is the holding-down plate or means through the holes of which the needles pass. The textile fiber fleece to be needled is passed between these two plates, with the barbed needles piercing the fiber fleece and thereby effecting the desired needling. The needles are mounted on a vertically reciprocated needle beam, whereby, depending on the piercing frequency, the air in the needle beam region is moved to a lesser or greater extent. The air masses moved by the needle beam herein pass with considerable acceleration through the holes in the holding-down means and then impinge on the fibers of the fiber fleece, with said fibers being more or less severely unsettled and particularly urged to the side, which results in irregular or irregularly thick and nonhomogeneous needle-bonded fabrics or fleeces, which detracts from the quality thereof.
Furthermore, it has been observed that particularly in the needling of regenerated fibers or of fibers obtained from reconstituted yarn fabrics, said fibers pass through the holes in the holding-down means during the processing, i.e. during the needling, and then collect on the upper side thereof, and this occurs in such great measure that they fill the space between the holding-down means and the needle beam so extensively that this at least leads to disruptions in operation, but often even to serious damage to the machine if it is not shut down and the fibers removed from between the holding-down means and the needle beam promptly enough. This causes a frequent and heavy expenditure for cleaning and supervision, not to mention the machine down times caused thereby.
To avoid the aforementioned disadvantages, i.e. on the one hand, to avoid the undesirable air flow through the holes in the holding down-means and, on the other hand, to avoid the passage of fibers through the holes in the holding-down means, a foam rubber layer covering said holes and pierced by the needles has been provided on the upper side of the holding-down means. The purpose of this foam rubber layer is to strip off fibers clinging to the barbs of the needles as the needles are withdrawn. To ensure the functioning of this construction it is necessary to cover the foam rubber layer on the upper side of the holding down-means with a perforated plate to prevent the foam rubber layer from prematurely wearing out and being destroyed by friction forces. This aforementioned construction is very costly and can only be maintained with considerable effort. Another disadvantage is that stripped off fibers collect in the needle passage openings in the holding-down means and clog them up, so that needle breakage occurs due to fiber clots formed in this way.